1. Field of the Invention
This invention pertains to a method for preparing silanes. More particularly, this invention pertains to a method for preparing ketoximosilanes containing a silicon bonded aminoalkyl radical.
2. Description of the Prior Art
Silanes containing two or more ketoximo groups bonded to silicon are known in the art. U.S. Pat. No. 3,189,576, which issued to Sweet on June 15, 1965 teaches preparing silanes corresponding to the formula EQU (X.dbd.NO).sub.a SiR.sub.4-a
by reacting a ketoxime of the formula X.dbd.NOH with a chlorosilane of the formula Cl.sub.a SiR.sub.4-a in the presence of an acid acceptor. The number of moles of ketoxime is at least equal to the number of moles of chlorine present in the silane. In these formulae X.dbd. represents R'.sub.2 C.dbd. or R"C.dbd., where R' represents a monovalent hydrocarbon radical or a monovalent halogenated hydrocarbon radical. R is selected from the group consisting of R', cyanoalkyl radicals and the hydrogen atom, R" represents a divalent hydrocarbon radical or a divalent halogenated hydrocarbon radical and a is 1, 2, 3, or 4.
The ketoximosilanes described by Sweet are useful curing agents for one-part moisture curable polyorganosiloxane compositions.
Japanese examined application No. 4837/85, which issued on Feb. 6, 1985, describes a method for preparing ketoximosilanes of the formula R.sub.a Si(NR'.sub.2).sub.b (ON.dbd.X).sub.4-a-b by the reaction of an alkylaminosilane of the general formula R.sub.a Si(NR'.sub.2).sub.4-a with a ketoxime of the formula X.dbd.NOH, where R represents an optionally substituted monofunctional aliphatic, alicyclic or aromatic hydrocarbon radical, R' is R or hydrogen, X is as defined hereinabove for the compounds of the aforementioned Sweet patent, a is 0 or 1, b is 0, 1, 2, or 3, and the sum of a and b is at most 3.
The silicon-nitrogen bond of the ketoximosilanes disclosed in the aforementioned Japanese patent publication would be expected to be unstable due to the relative ease with which a silicon-nitrogen bond can be hydrolyzed.
For some end use applications it would be desirable to have a ketoximosilane containing a primary or secondary amino group that is bonded to silicon through carbon rather than through nitrogen as in the compounds of the aforementioned Japanese patent publication. The amino group provides the means to incorporate a ketoximosilyl group into organic polymers and silicone/organic copolymers containing amine-reactive groups such as isocyanate. The resultant polymers would cure in the presence of atmospheric moisture.
An objective of this invention is to provide a method for preparing ketoximosilanes containing a primary or secondary amino group that is bonded to the silicon atom of the silane by means of a carbon atom.